This invention relates to an entry alarm system for vehicles such as automobiles, trucks, buses and motor homes, activated by unauthorized opening of vehicle closures.
While entry alarm systems for such vehicles are known, such systems are frequently cumbersome and difficult to install in an existing vehicle, resulting in expense which is prohibitive of widespread use of such systems.
A disadvantage of some such known systems, which sound a warning in the event of unauthorized opening of a door, trunk lid, or hood for example, is that the systems require a key operated external deactivation switch to prevent sounding of the vehicle alarm through normal entry of the vehicle or trunk by the owner or other authorized user. This is a great inconvenience and disadvantage in that the user must always deactivate the system before entering his vehicle and, correspondingly, must reactivate the system after leaving his vehicle. This is time consuming and inconvenient; and the system is entirely defeated in the event the user should forget to reactivate the system upon leaving the vehicle.
An object of this invention is to provide a vehicle burglar alarm system which is completely automatic in operation, and does not require the use of a deactivation switch.
Another object of this invention is to provide a burglar alarm control system which is readily adapted to be installed in existing vehicles, and to be easily connected to existing operating circuits of the vehicle.
A further object of this invention is to provide an alarm control system which utilizes the vehicle horn and which, in a mischief situation, sounds the vehicle horn intermittently to warn of such mischief situation.
These objects are accomplished in a control circuit which is adapted for connection to the vehicle horn circuit, the vehicle ignition switch circuit, and a closure switch circuit which includes a light switch for a door, a trunk deck lid, or a hood, and which is completely automatically operated by the circuits to which it is connected. The control circuit includes the following subcircuits. An output circuit includes a transistor switch for energizing the alarm device. A signal generator circuit for generating a control signal has its output coupled to the base of the transistor switch. A diversion circuit includes a normally closed switch, for directing the signal generator circuit output to effect shut-off of the output circuit transistor switch. A closure control circuit and an ignition control circuit, connected respectively to the vehicle closure switch circuit and ignition switch circuits, are responsive to the open condition of both the vehicle closure switch and ignition switch to maintain the diversion circuit switch closed; and are responsive to the closed condition of the vehicle closure switch and open condition of the ignition switch to effect the opening of the diversion circuit switch. The opening of the diversion circuit switch effects the closing of the output circuit transistor switch to effect energization of the alarm device.
The novel features and the advantages of the invention, as well as additional objects thereof, will be understood more fully from the following description when read in connection with the accompanying drawings.